1. Field of the Invention
The present invention relates to a plunger pump activated by a motor.
2. Background Art
Hitherto, as an automobile brake mechanism, an antilock brake mechanism (so-called ABS) is known. The antilock brake mechanism realizes stable braking by, for example, controlling a fluid pressure of a hydraulic fluid supplied to a brake at the time of braking on a slippery road surface. The antilock brake mechanism drives, in order to control the fluid pressure of a hydraulic fluid, a plunger pump by rotation of an electric motor (see JP-A-2000-179449, for example).
Such an antilock brake mechanism includes an electronic control unit and a fluid-pressure control unit. The electronic control unit controls operation of various solenoid valves of the fluid-pressure control unit and the electric motor based on information from various sensor systems, for example, a wheel speed sensor. An eccentric shaft portion is provided in a rotating shaft of the electric motor, and on the outer circumference of the eccentric shaft portion, a ball bearing is fitted as a drive member. By urging a plunger by a spring member so as to be always brought in contact with this ball bearing and turning the rotating shaft, the plunger is reciprocated to discharge a hydraulic fluid so as to generate a fluid pressure.
However, in such a plunger pump, a further improvement has been demanded in electric motor vibration due to the eccentric shaft portion and operation noise due to a pulsation of the hydraulic fluid discharged from the plunger pump.